Throttle valves in throttle valve connectors are known. In DE 195 12 729 A1, a throttle valve connector having a tubular housing is described, in which a throttle valve is fastened to a throttle valve shaft, which is mounted at its free ends such that it can be rotated transversely with respect to the longitudinal axis of the tubular housing, leading through cutouts in the housing wall. When arranging throttle valves in throttle valve connectors, it is often disadvantageous that, on account of to some extent extremely small leakage stipulations, it is necessary to operate with high precision and surface quality. In this case, casting material, of which the throttle valve connector is composed, and the casting quality have a high quality standard. The throttle valve in this case is generally punched out of a metal sheet and turned extremely finely with great effort in terms of precision, very close tolerances having to be maintained.
A method according to the preamble of claim 1 is disclosed by FR 2 687 601 A1. There, in the region of the shaft aperture, a critical transition region between throttle valve and throttle valve connector results.
JP 11 229909 A discloses a throttle valve connector having a peripheral projection, while DE 199 18 777 A1 indicates the injection molding of a shaft having valve wings for a control valve unit.
The invention is based on the object of providing a method for production of a throttle valve in a continuous throttle valve connector in which it is possible to dispense with a turning operation in the close tolerance range.
The object on which the invention is based is achieved by a method for production of a throttle valve in a continuous throttle valve connector. First of all, use is made of a throttle valve connector of a first plastic which, on the inside, has a peripheral projection running toward the center of the throttle valve connector. Then, via the apertures, a throttle valve shaft is introduced through the throttle valve connector and the plastic insert, at right angles to the longitudinal axis of the throttle valve connector, is mounted in the apertures in each case by a first hollow plug and a second hollow plug, with which the apertures in the throttle valve connector are closed in a manner complementary to the plastic insert and, from both sides, a first die and a second die are introduced into the throttle valve connector which, between the two of them and the peripheral projection of the plastic insert that is formed and runs toward the center of the throttle valve connector, form a second cavity which surrounds the throttle valve shaft in the form of the throttle valve; then, in a further step, a molten second plastic is put into the second cavity through the first die and is cured there, forming the throttle valve; then, in a still further step, the first die and the second die are removed from the throttle valve connector. The first plastic is put into the first cavity through at least one aperture.
This means that in every case there are two apertures but only one aperture has to serve as a feed line for the first plastic. However, it is also possible to put the first plastic into the first cavity through both apertures. During the curing of the second plastic, the throttle valve is necessarily connected to the throttle valve shaft. This takes place as a result of shrinkage of the second plastic during the cooling phase. The throttle valve shaft is in each case mounted in the apertures by a first hollow plug and a second hollow plug which, for example, are configured in the form of tubular pieces sealed off on one side. They generally consist of steel.
A preferred development of the method provides that, in a first step, a peripheral, annular groove is machined in the throttle valve connector; then, in a second step, a third die and a fourth die are introduced into the throttle valve connector from both sides, being configured so as to be complementary to each other and, when introduced, forming in the region of the annular groove a cylindrical first cavity which, toward the center of the throttle valve connector, has a peripheral projection; then, in a third step, a molten first plastic is put into the first cavity laterally through at least one aperture in the throttle valve connector and is cured there, forming a plastic insert; then, in a fourth step, the third die and the fourth die are removed from the throttle valve connector. The throttle valve connector can consist, for example, of die cast aluminum. The peripheral, annular groove machined into the throttle valve connector can be bounded on one side or two sides, parallel to the longitudinal axis of the throttle valve connector. The first die, the second die, the third and fourth die consist of steel.
The third die and the fourth die are configured so as to be complementary to each other. This means that they interact functionally and jointly form the cylindrical cavity, the peripheral projection of this cylindrical cavity being formed by their end faces which make contact when introduced, by removal of material there. This peripheral projection can be annular.
The first plastic differs from the second plastic by its shrinkage capacity during the cooling phase. This achieves a situation where a slight gap is formed between the throttle valve produced and the plastic insert, so that the throttle valve cannot be joined to the plastic insert. In the fourth step, the apertures of the throttle valve connector are closed so as to be complementary to the plastic insert. This is carried out by means of the introduction of the first hollow plug and of the second hollow plug into the apertures. As a result, delimitation of the peripheral projection of the plastic insert running toward the center of the throttle valve connector is achieved, said insert no longer being present at the location of the apertures. The second plastic is normally put into the throttle valve connector via a hole running centrally through the first die.
It has surprisingly transpired that, in the method for production of a throttle valve in a continuous throttle valve connector, no kind of turning operations are necessary in which the setting of small tolerances is carried out. The technical interplay between throttle valve and plastic insert in the throttle valve connector is implemented solely by the two injection molding operations in the continuous throttle valve connector, so that complicated remachining steps can be dispensed with.
A preferred refinement of the invention consists in the peripheral projection of the plastic insert not being formed continuously at the same spacing from the edges of the plastic insert, and the maximum angle α between the perpendicular to the longitudinal axis of the throttle valve connector and the direct connection between two directly mutually opposite regions of the peripheral projection lying between 7° and 8°. In this way, the generally desired oblique position of the throttle valve in the continuous throttle valve connector is achieved in a straightforward manner. The end faces of the first die and of the second die are in this case designed to run obliquely in a complementary manner.
According to a further preferred refinement of the invention, the first plastic and the second plastic used are polyphenyl sulfide (PPS) with different linear coefficients of expansion. This polyphenyl sulfide is particularly suitable for production of the throttle valve on account of its shrinkage behavior.
According to a further refinement of the invention, provision is made for the first plastic used to be a polyphenyl sulfide (PPS) with a linear coefficient of expansion between 90 and 250° C. of 36·10−6 and the second plastic used to be a polyphenyl sulfide (PPS) with a linear coefficient of expansion between 90 and 250° C. of 46·10−6. These two types of plastic are particularly advantageously suitable for the intended use.
A further preferred refinement of the invention consists in a throttle valve shaft being introduced which has a tapered cross section in the region of the throttle valve. In this case, the taper advantageously corresponds to the thickness of the second plastic on the throttle valve shaft, so that the latter terminates flush with the actual diameter of the throttle valve shaft. As a result, a larger projection of the throttle valve shaft beyond the actual diameter of the throttle valve shaft is advantageously avoided. Furthermore, it is ensured that the arrangement of the throttle valve on the throttle valve shaft is associated with only a relatively low space requirement.
According to a further preferred refinement of the invention, a throttle valve shaft is introduced which, in the region of the throttle valve, has machined portions for the form-fitting fixing of the second plastic. These machined portions can be, for example, roughened portions, protrusions, external threads or grooves, into which the second plastic is introduced and is cured there. By means of this form-fitting fixing, the joint between the throttle valve and the throttle valve shaft is reinforced.
According to a further refinement of the invention, the machined portions provided are holes. In this case, it is particularly advantageous to provide two continuous holes arranged beside each other on the throttle valve shaft, into which the molten second plastic penetrates during the injection molding and can likewise cure there, which noticeably improves the stability of the joint between the throttle valve and the throttle valve shaft.